Continent

A continent (Latin continere, "to hold together") is a large continuous land mass. There are several conceptions of what a continent is, geographic, geologic, and tectonic.

Geologic continents

Geologically, the surface of Earth consists of many tectonic plates, consisting of rigid lithospheric mantle and crust moving together over the much less viscous asthenosphere. Continental crust is primarily granitic in composition, overlain by sedimentary and metamorphic rocks. Much of the continental crust extends above sea level as dry land. Oceanic crust is basaltic in composition, and much thinner than continental crust, thus generally lying below sea level.

Related Topics:
Geologically - Earth - Tectonic plate - Lithospheric - Asthenosphere - Granitic - Sedimentary - Metamorphic rock - Sea level - Basaltic

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Although from a human perspective shallow inland seas such as the Bering Sea appear to divide up land masses into continents, such ephemeral features do not define continents geologically. For instance, many times over the past few million years, the continents of Eurasia and America were connected by dry land. A geologic continent, therefore, is a continuous piece of continental crust, whether wet or dry at a particular time. As such, Laurasia and Africa-Arabia are one continent, which for the past three million years has also been linked to South America. This world-spanning land mass has no name except for the Classical meaning of "The Continent". The other large geologic continents are Sahul and Antarctica, but there are many so-called microcontinents as well: Madagascar, the Seychelles (the northern Mascarene Plateau), New Zealand, New Caledonia, etc., which are splinters of the ancient supercontinent of Gondwana. Note that volcanic Iceland is an exposed bit of oceanic crust at the mid-ocean ridge, and therefore not a microcontinent. Likewise, the British Isles, Sri Lanka, Borneo, and Newfoundland are integral parts of the Laurasian continent which happen to be separated by shallow (and temporary) inland seas flooding its margins.

Related Topics:
Bering Sea - Arabia - Microcontinent - Madagascar - Seychelles - Mascarene Plateau - New Zealand - New Caledonia - Gondwana - Iceland - Mid-ocean ridge - British Isles - Sri Lanka - Borneo - Newfoundland

~ ~ ~ ~ ~ ~ ~ ~ ~ ~